It didn't cost anything--we did buy a tour for the equipment and the ride out there, though.
Depends where you are departing from.
The water level in Hanauma Bay is not equal. If we speak generally, it is from 2 feet to 11 feet in places.
It depend on the size and the type of window. The cheapest is going to be around $400 and you can just about spend as much as you want.
255 - 308 g
about 12 hours 41 mins